Stock-Based Compensation

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

NOTE 9.  STOCK-BASED COMPENSATION

Stock-based compensation granted under our Company’s stock plans is expensed in tranches over the vesting period. Non-performance based grants generally vest equally over a three or four-year period. Performance units generally cliff vest three years after they are granted. Each performance unit and restricted stock unit represents a contingent right to receive one share of Common Stock as of the vesting date. Such Common Stock may be subject to forfeiture for the payment of any required tax withholding.

The activity related to our Company's restricted stock unit awards was as follows:

	Three Months Ended March 31, 2018
	Number of Awards			Weighted Average Grant Date Fair Value (1)
Nonvested at the beginning of the period		159,539		$	41.60
Granted		20,593		$	48.70
Vested (2)		(13,986	)	$	39.71
Forfeited		(7,000	)	$	38.00
Nonvested at the end of the period		159,146		$	42.84

(1) Fair value is based on the closing price of our common shares on the NASDAQ on the grant date.

(2) This amount represents the gross number of shares vested before any share forfeiture to pay required tax withholdings. For the three months ended March 31, 2018 share awards of 5,782 were withheld for tax payments at a weighted average vest date fair value of $48.97.

The activity related to our Company's performance-based equity awards was as follows:

	Three Months Ended March 31, 2018
	Number of Awards			Weighted Average Grant Date Fair Value (1)
Nonvested at the beginning of the period		966,361		$	43.39
Granted		247,554		$	54.15
Performance Adjustment		(59,833	)	$	37.25
Vested (2)		(274,299	)	$	37.25
Forfeited		(15,250	)	$	42.45
Nonvested at the end of the period		864,533		$	48.86

(1) Fair value is based on the closing price of our common shares on the NASDAQ on the grant date.

(2) This amount represents the gross number of shares vested before any share forfeiture to pay required tax withholdings. For the three months ended March 31, 2018 share awards of 117,005 were withheld for tax payments at a weighted average vest date fair value of $55.65.